1. Technical Field
The present invention relates to a ball retainer suitable especially for the bearing of the rotating portion of so-called office automation equipment (OA equipment), and a ball bearing including the same.
2. Description of the Prior Art
The ball bearing includes a retainer for disposing balls at the appropriate position between inner and outer rings thereof.
In the crown shaped retainer of the prior art as shown in FIG. 8, a plurality of pockets 22 for retaining balls are provided circumferentially at equal intervals around an annular body 21.
Each pocket includes an entrance 23 defined by a pair of opposite claws 24, 24.
The inner peripheral surface of the pocket has a spherical shaped inner peripheral surface corresponding substantially to the surface of the ball to be retained therein.
In the retainer of the prior art of the above-mentioned type, the thickness d of the body is enlarged to increase the strength and the rigidity thereof. Thus the surface area of the inner periphery of the pocket is increased so that the frictional resistance to be exerted on the ball through the contact with the inner peripheral surface of the pocket is also increased.
The frictional resistance will also be increased by the fact that the shape of the spherical shaped inner peripheral surface of the pocket is similar to the surface of the ball.
The object of the present invention is to reduce the size of the pockets of the ball bearing without lowering the rigidity of the retainer through the reduction of the contact area between a ball and a retainer.
Another object of the present invention is to provide a substantially triangular shaped lubricant reservoirs between the ball and a junction between the upper and lower half of the pocket, and a junction between the lower half and the bottom portion of the pocket.
In order to attain the object of the present invention, in accordance with the first aspect of the present invention, a retainer includes an annular retainer body, a plurality of pockets for retaining the balls therein disposed around the retainer body, and a ball entrance of each pocket defined by a pair of opposite slightly elastic claws formed on one of the outer edges of the retainer body, the retainer being characterized in that each pocket includes substantially upper left and right halves following the entrance, a pair of right and left lower halves following the upper halves, and a bottom portion disposed between lower halves, wherein, an inner peripheral surface of each upper half presents a curved surface of the pocket of the radius of curvature slightly larger than that of the ball to be retained therein in both peripheral and width directions, an inner peripheral surface of each lower half descending inwardly toward the junction with the bottom portion of the pocket presents a configuration which has a shape of curved surface in the width direction of the pocket and of a straight shape in the peripheral direction of the pocket so as to contact tangentially with the ball, and an inner surface of the bottom presents a configuration which has a shape of curved surface in the width direction in the same way as those of the upper and lower halves, and is straight shape in the peripheral direction of the pocket so as to contact tangentially with the ball to be retained.
The retainer for a ball bearing according to the present invention is further characterized in that the thickness of a portion of the retainer around the pocket is reduced, and the thickness of a portion of the retainer other than the portion around the pocket is enlarged, said claws have an elasticity sufficient to allow the ball to push them apart to get into the pocket, and said retainer is made of synthetic resin.
In accordance with the second aspect of the present invention, a ball bearing including a retainer, plurality of balls an inner ring and an outer ring, the retainer includes an annular retainer body, a plurality of pockets for retaining the balls therein disposed around the retainer body, and a ball entrance of each pocket defined by a pair of opposite slightly elastic claws formed on one of the outer edges of the retainer body, the retainer being characterized in that each pocket includes substantially upper left and right halves following the entrance, a pair of right and left lower halves following the upper halves, and a bottom portion disposed between lower halves, wherein, an inner peripheral surface of each upper half presents a curved surface of the pocket of the radius of curvature slightly larger than that of the ball to be retained therein in both peripheral and width directions, an inner peripheral surface of each lower half descending inwardly toward the junction with the bottom portion of the pocket presents a configuration which has a shape of curved surface in the width direction of the pocket and of a straight shape in the peripheral direction of the pocket so as to contact tangentially with the ball, an inner surface of the bottom presents a configuration which has a shape of curved surface in the width direction in the same way as those of the upper and lower halves, and is straight shape in the peripheral direction of the pocket so as to contact tangentially with the ball to be retained, and the retainer is assembled between the inner ring and the outer ring and the balls are retained within the pockets.
The ball bearing according to the present invention is further characterized in that the thickness of a portion of the retainer around the pocket is reduced, and the thickness of a portion of the retainer other than the portion around the pocket is enlarged, said claws have an elasticity sufficient to allow the ball to push them apart to get into the pocket, said retainer is made of synthetic resin, and lubricant reservoirs of substantially triangular configuration are defined between the ball and a junction between the upper and lower half of the pocket, and a junction between the lower half and the bottom portion of the pocket.